Widely utilized, aromatherapy is employed for relief of pain, relaxation and anxiety reduction. Despite its popularity, efficacy data are scant, and potential mechanisms of action are controversial. This project will examine the behavioral, autonomic, endocrine, and immune consequences of one sedating or relaxant odor, Lavandula augustifolia, one activating or stimulant odor, Citrus limonum, and a no-odor (distilled water) control in men and women during both resting and "challenge" or stress conditions. In each case we will measure several different aspects of the cellular immune response, as well as skin barrier repair following tape stripping. This design will allow us to examine the ability of the odors to modulate autonomic, endocrine, and immune function, and health-relevant cutaneous responses. Importantly, contextual variables such as expectancies and positive evaluations of odors are likely to be central to responsiveness in humans; thus we will also evaluate responses using a battery of unobtrusive behavioral measures as well as standard self-report measures. Accordingly, the specific aims of the proposed study are: 1) to determine if there are reliable differences in behavioral, autonomic, endocrine, immune, and cutaneous responses to sedative and stimulant essential oils, and if behavioral and physiological responses to both relaxant and stimulant odors differ from a no-odor control condition; 2) to determine the extent to which an individual's expectancies and mood (anxiety and depressive symptoms) prior to olfactory exposure influences behavioral and physiological responses to sedative and stimulant essential oils, as well as the extent to which self-reported pleasure or liking for an odor influences responsiveness; 3) to assess changes in behavioral, autonomic, endocrine, immune, and cutaneous responses to sedative and stimulant odors during resting and challenge conditions; and 4) to determine the extent to which gender influences olfactory thresholds, as well as behavioral and physiological responsiveness to odors. If the essential oils used in aromatherapy are indeed immunomodulatory as well as mood-enhancing as practitioners suggest, then the greatest clinical benefits are likely to be seen under stress, via the restoration or enhancement of immune function. Accordingly, a psychoneuroimmunology focus for these mechanistic studies will provide a way to clarify mechanisms while assessing clinical efficacy.